Robot and Servo Drive Lab. Regenerative Braking System of Electric Vehicle Driven by Brushless DC Motor IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL. 61, NO. 10, OCTOBER 2014 By Xiaohong Nian, Fei Peng, and Hang Zhang Department of Electrical Engineering Southern Taiwan University of Science and Technology 2016/3/24 Outline Simulation Results Abstract Conclusion Introduction References Motor And Control BLDC Motors BLDC Motor Control MOSFET Control of Regenerative EV Modeling Optimal Braking Performacne And RBS Efficiency 2016/3/24 Department of Electrical Engineering Robot and Servo Drive Lab. Southern Taiwan University of Science and Technology 2 Abstract Regenerative braking can improve energy usage efficiency and can prolong the driving distance of electric vehicles (EVs). In this paper, BLDC motor control utilizes the traditional roportional–integral–derivative (PID) control. The simulation results show that the fuzzy logic and PID control can realize the regenerative braking and can prolong the driving distance of EVs under the condition of ensuring braking quality. At last, it is verified that the proposed method is realizable for practical implementation. 2016/3/24 Department of Electrical Engineering Robot and Servo Drive Lab. Southern Taiwan University of Science and Technology 3 Introduction Regenerative braking can be used in EVs as a process for recycling the brake energy, which is impossible in the conventional internal combustion vehicles. 2016/3/24 Department of Electrical Engineering Robot and Servo Drive Lab. Southern Taiwan University of Science and Technology 4 BLDC Motors Brushless dc (BLDC) motors are ideally suitable for Evs because of their high power densities, good speed-torque characteristics, high efficiency, wide speed ranges, and low maintenance. BLDC motor is a type of synchronous motor. It means that the magnetic field generated by the stator and the magnetic field generated by the rotor rotation are at the same frequency. 2016/3/24 Department of Electrical Engineering Robot and Servo Drive Lab. Southern Taiwan University of Science and Technology 5 BLDC Motors Knowledge of rotor position is critical to sustaining the motion of the windings correctly. The information of rotor motion is obtained either from Hall effect sensors or from coil EMF measurements Fig. 2. Fig. 2. Back EMF BLDC motor phase. 2016/3/24 Department of Electrical Engineering Southern Taiwan University of Science and Technology 6 BLDC Motor Control BLDC motor control is the main control of the electronic commutator (inverter), and the commutation is achieved by controlling the order of conduction on the inverter bridge arm a typical H-bridge is shown in Fig. 3. 2016/3/24 Fig. 3. H-bridge inverter circuit. Department of Electrical Engineering Robot and Servo Drive Lab. Southern Taiwan University of Science and Technology 7 BLDC Motor Control The BLDC voltage vector is divided into six sectors, which is just a one-to-one correspondence with the Hall signal six tates, as illustrated. 2016/3/24 Department of Electrical Engineering Robot and Servo Drive Lab. Southern Taiwan University of Science and Technology 8 MOSFET Control of Regenerative Regenerative braking can be achieved by the reversal of current in the motor-battery circuit during deceleration, taking advantage of the motor acting as a generator, redirecting the current flow into the supply battery. Due to the presence of inductances in motor windings, these inductances in the motor can constitute the boost circuit. 2016/3/24 Department of Electrical Engineering Robot and Servo Drive Lab. Southern Taiwan University of Science and Technology 9 MOSFET Control of Regenerative Fig. 5 shows the phase relation among the back EMF, the armature current of the BLDC motor, and the switching signals for the bidirectional dc/ac converter. Fig. 5. Regenerative braking with single switch. 2016/3/24 Department of Electrical Engineering Robot and Servo Drive Lab. Southern Taiwan University of Science and Technology 10 By controlling MOSFET, the whole circuit constitutes a boost circuit. 2016/3/24 Fig. 6. Equivalent circuit of the single switch. Department of Electrical Engineering Robot and Servo Drive Lab. Southern Taiwan University of Science and Technology 11 According to the principle of the volt-second balance, one can conclude that the net change in the equivalent inductor voltage vL is zero over one electric cycle, i.e., 2016/3/24 Department of Electrical Engineering Robot and Servo Drive Lab. Southern Taiwan University of Science and Technology 12 2016/3/24 Department of Electrical Engineering Robot and Servo Drive Lab. Southern Taiwan University of Science and Technology 13 Fig. 7. Maximum conversion ratio versus K for regenerative braking with single switch. 2016/3/24 Department of Electrical Engineering Robot and Servo Drive Lab. Southern Taiwan University of Science and Technology 14 EV Modeling The modeling of the EV has been done in MATLAB/ Simulink. The driver block makes a torque request which propagates through various powertrain system component and realizes vehicle motion. 2016/3/24 Department of Electrical Engineering Fig. Southern Taiwan University of Science and Technology 15 8. Structure of the control strategy system. Where mv is the vehicle mass (in kilograms), v is the vehicle speed (in meters per square second), Fa is the aerodynamic friction (in newtons), Fr is the rolling friction (in newtons), and Fg is the force caused by gravity when driving on nonhorizontal roads (in newtons). 2016/3/24 Department of Electrical Engineering Robot and Servo Drive Lab. Southern Taiwan University of Science and Technology 16 Aerodynamic Friction Losses: Rolling Friction Losses: Uphill Driving Force: 2016/3/24 Department of Electrical Engineering Robot and Servo Drive Lab. Southern Taiwan University of Science and Technology 17 Fuzzy Control The fuzzy control strategy of the EV braking force distribution structure is shown in Fig. 8; the three inputs are the EV frontwheel braking force, speed, and battery charge state [state of charge (SOC)]. 2016/3/24 Department of Electrical Engineering Southern Taiwan University of Science and Technology 18 Membership functions of fuzzy control. (a) Membership function of the front braking force. (b) Membership function of the SOC. (c) Membership function of speed. (d) Membership function of ratio. Department of Electrical Engineering Robot and Servo Drive Lab. Southern Taiwan University of Science and Technology 19 Fuzzy control rules: the front braking force is L, M, and H; SOC is L, M, and H; and speed is L and H. We prefer the rules 2016/3/24 Department of Electrical Engineering Robot and Servo Drive Lab. Southern Taiwan University of Science and Technology 20 PID Control With PID control used primarily to ensure a constant brake torque, different braking force values will give different PWMs. It is supposed that PID control can quickly adjust the desired PWM in order to maintain braking torque constantly. When the fuzzy reasoning is slower than PID control, the braking torque can be real-time controlled by PID control . 2016/3/24 Department of Electrical Engineering Robot and Servo Drive Lab. Southern Taiwan University of Science and Technology 21 Optimal Braking Performacne And RBS Efficiency The fully controllable hybrid brake system can be controlled to apply braking forces on the front and rear wheels by following the ideal braking force distribution curve (Fig. 11). 2016/3/24 Department of Electrical Engineering Robot and Servo Drive Lab. Southern Taiwan University of Science and Technology 22 The following equations describe the battery’s SOC at discharge and charge. At discharge 2016/3/24 Department of Electrical Engineering Robot and Servo Drive Lab. Southern Taiwan University of Science and Technology 23 In the braking process on a flat road, the vehicle’s kinetic energy and regenerative electrical energy are calculated by the following: 2016/3/24 Department of Electrical Engineering Robot and Servo Drive Lab. Southern Taiwan University of Science and Technology 24 Simulation Results 2016/3/24 Simulation EV speed curve. Department of Electrical Engineering Robot and Servo Drive Lab. Southern Taiwan University of Science and Technology 25 Simulation EV speed curve. 2016/3/24 Department of Electrical Engineering Robot and Servo Drive Lab. Southern Taiwan University of Science and Technology 26 2016/3/24 Simulation EV speed curve. Department of Electrical Engineering Robot and Servo Drive Lab. Southern Taiwan University of Science and Technology 27 Braking force distribution. Energy regeneration when braking. 2016/3/24 Department of Electrical Engineering Robot and Servo Drive Lab. Southern Taiwan University of Science and Technology 28 Current curve on the BLDC motor dc bus with PID control. 2016/3/24 Department of Electrical Engineering Robot and Servo Drive Lab. Southern Taiwan University of Science and Technology 29 2016/3/24 Battery’s SOC change. Department of Electrical Engineering Robot and Servo Drive Lab. Southern Taiwan University of Science and Technology 30 DC bus voltage of different duties but at the same speed. 2016/3/24 Department of Electrical Engineering Robot and Servo Drive Lab. Southern Taiwan University of Science and Technology 31 DC bus voltage at the same speed. 2016/3/24 Department of Electrical Engineering Robot and Servo Drive Lab. Southern Taiwan University of Science and Technology 32 2016/3/24 Voltage, current, and speed waveforms at the breaking state. Department of Electrical Engineering Robot and Servo Drive Lab. Southern Taiwan University of Science and Technology 33 Conclusion This paper has presented the RBS of EVs which are driven by the BLDC motor. The performance of the EVs’ egenerative brake system has been realized by our control scheme which has been implemented both in the simulation and in the experiments. Therefore, it can be concluded that this RBS has the ability to recover energy and ensure the safety of braking in different situations. 2016/3/24 Department of Electrical Engineering Robot and Servo Drive Lab. Southern Taiwan University of Science and Technology 34 References [1] P. J. Grbovic, P. Delarue, P. Le Moigne, and P. Bartholomeus, “A bidirectionalthree-level dc-dc converter for the ultracapacitor applications,”IEEE Trans. Ind. Electron., vol. 57, no. 10, pp. 3415–3430, Oct. 2010. [2] F. Wang, X. Yin, H. Luo, and Y. Huang, “A series regenerative brakingcontrol strategy based on hybrid-power,” in Proc. Int. Conf. CDCIEM, 2012, pp. 65–69. [3] N. Mutoh and Y. Nakano, “Dynamics of front-and-rear-wheelindependent-drive-type electric vehicles at the time of failure,” IEEE Trans. Ind. Electron., vol. 59, no. 3, pp. 1488–1499, Mar. 2012. [4] M. Cheng, W. Hua, J. Zhang, and W. Zhao, “Overview of statorpermanentmagnet brushless machines,” IEEE Trans. Ind. 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